1. Field of the Invention
The subject invention is generally related to modular systems for work functions on a drilling or production rig or platform and is specifically directed to the composition, operation, and performance of a skid based modular system for coiled tubing and similar operations.
2. Discussion of the Prior Art
Various operations are routinely performed on drilling and production platforms. Each of the operations includes subsets of equipment and specific operational functions associated with the equipment. By way of example, a coiled tubing operation includes a plurality of different processes or sequences of actions, some of which can be viewed as general to the service and some of which can be viewed as specific to the particular system used. The general process components include positioning equipment on the platform, assembling the equipment, stabbing tubing, pressure testing well control equipment and similar functions incorporated regardless of the specific equipment used. Specific functions are dictated by the particular equipment and system being utilized.
The deployment of coiled tubing pressure control and conveyance equipment in offshore environments is a time consuming process made complicated by spatial constraints, crane lifting limitations, safety considerations and intensive assembly on location. The majority of coiled tubing systems utilized offshore to date incorporate virtually no pre-assembly of system components making the Rig Up process extremely inefficient. This is particularly true for systems utilizing the multiple pressure control components required to perform high pressure work.
A constant in all systems is the requirement that the various components of the system be moved into place, assembled and tested prior to initiation of the operation. In the industry, this is generally referred to as xe2x80x9cRig Upxe2x80x9d work. The amount of time and expense involved in Rig Up work is substantial and dramatic increases in profitability of the rig can be achieved with small time savings in repetitive Rig Up operations.
Very little integration of conveyance and pressure control equipment is currently utilized offshore. Coiled tubing jacking frames are currently used in offshore environments to support and manipulate coiled tubing conveyance equipment. The typical CT jacking frame consists of a four-post support system containing a one or two-dimensional in-plane translation type table into which the injector is inserted. The injector support can also be raised or lowered. One type of system also possesses a rotation table for aligning the injector gooseneck with the reel. Due to spatial transport restriction, the injector and jacking frame are transported separately onto the platform. Pressure control equipment including BOPs, riser sections and strippers are separately lifted into appropriate positions in the well stack. In the prior art systems, a minimum of seven components must be separately installed on location.
The principal hindrance in the Rig Up of existing coiled tubing systems is the need to assemble virtually every component in the system on location. This fragmentation of the operation results in numerous crane lifts to move equipment components into position and numerous assembly steps to couple these components together.
A major drawback to pre-rigging or assembly prior to Rig Up is the sheer size of the equipment being utilized. In order to achieve maximum benefit by pre-assembly the equipment must fit reasonable transportation dimensions.
To date, there are not any available systems that permit comprehensive pre-rigging at an offsite location. It is desirable that such a system be developed for increasing safety by eliminating repeated make-up and break-down of critical assemblies, and by permitting increased efficiency in installing such systems for operation. It is also desirable that such a system be developed to permit transport to and from a rig in standard transport systems and containers in its assembled state.
The subject invention is directed to a modular, pre-assembled system for rig workovers, and the preferred embodiment is a modular, pre-assembled system specifically designed for coiled tubing operations. The system of the subject invention results in improved equipment utilization and in significant improvements in time, personnel and safety issues. The system also improves safety and environmental concerns by minimizing Rig Up time through the ability to pre-assemble many critical safety components off rig and in controlled factory environment.
One important aspect of the invention is that the use of pre-assembled modular components frees up the rig crane, always a bottleneck in offshore work. By permitting a plurality of pre-assembled components to be transported into and out of operational position, the time required by the rig crane is substantially reduced.
Specifically, the subject invention is directed to a modular work system permitting Rig Up time to be substantially reduced by reducing the number of crane lifts required to offload equipment from a transport boat or other transport vehicle. This is achieved by developing transport skids capable of holding multiple system components. The invention is also directed to reducing the number of crane lifts required to position equipment on the platform. One objective of the present invention to reduce the number of equipment components that must be mechanically coupled on location by pre-assembling the components and maintaining the assembly in operating condition during storage and transport. This pre-assembly also applies to hydraulic and other control lines. An additional advantage of the system of the subject invention is the reduction of personnel time and numbers required to support the operation on the rig.
In order to achieve the objectives of the invention, skid design concepts are employed, wherein a skid system carries various pre-assembled components for transport, storage and operation. Specifically, a skid sub-system includes various related components. The components are either pre-assembled or are designed to complete a sub-assembly through final assembly on the rig. The skid is moved into place using the crane, and the assembly is completed. Additional sub-systems are mounted on additional skids which are designed to be mated with other related skids and sub-assemblies.
It is an important aspect of the invention that each skid sub-system fit within specific size or space constraints in order to meet transportation regulations for vehicle width and height. By way of example, standard offshore containers have widths of 2.5 m and height of 2.8 m. Skid height may also be a function of the trailer deck height. For example, Norwegian transport laws stipulate that a truck cannot be more than 4.0 m in height. Obviously, a xe2x80x9clow-boyxe2x80x9d trailer with a deck height of 0.5 m will permit a taller or higher skid height than a standard trailer with a deck height of 1.0 m. Skid length is also dictated by useful trailer length, which is typically, about 6.0 m. Weight is also a factor, both for transportation and crane lifting functions. Each skid is preferably designed to incorporate the maximum amount of equipment required for a particular job, while remaining within the various size and weight limits imposed on the transport of such equipment.
A preferred embodiment of the invention is directed to a coiled tubing operating system and comprises nine pre-assembled skid components, namely, the control cabin, power pack, reel, power stand, jacking frame, blowout preventer (BOP) transport frame, BOP accumulator/control skid, shaker tank and workshop container. Efficient rig-up is accomplished by having the riser and triple BOP components travel assembled and by having the tubing injector travel assembled to the jacking frame and stripper, preferably with the gooseneck attached. The system is designed to be set up with a minimum of connections between skid units, thereby greatly increasing efficiency, as well as making the various Rig-Up operations safter through the use of factory assembled and tested connections and components.
In the past, assembly of the well control stack and injector was identified as being one of the most time consuming parts of the Rig Up process. The subject invention for the jacking frame travels with the injector and stripper assembled and the gooseneck attached, but folded to meet envelope requirements, with an objective of significantly reducing setup time associated with these components. The BOP transport skid is designed to mechanically interface with the jacking frame and skid, eliminating the need to rely on the orientation of the frame to the deck to assure coupling accuracy. That is, the BOP skid forms a support base for the jacking frame. Both components are designed to permit proper mating and interconnectivity. This assures efficient and accurate connections.
In the preferred embodiment of the invention, the injector is supported on a platform with a skid-plate that allows rotation about the vertical axis. The injector platform is attached to single columnar support adapted for vertical translation. The base of the support travels on a rail system to permit horizontal motion and placement.
In those cases where the overall height exceeds transportation requirements, each assembly is designed to travel on it""s side and may be pivoted into operating position during Rig Up.
In a preferred embodiment of the invention, the jacking system provides four axis motion of the injector. The system can raise and lower the injector to provide a work window between the stripper and BOP. The jacking frame is designed to allow transfer of all operation induced vertical load to the wellhead. The jacking system will provide the required motion while supporting the injector, stripper and gooseneck. The jacking system includes work decks and handrails for access to the service areas of the injector. The system is designed for quick and simple deployment. Ladders may be included in the integral system.
The jacking system or jacking fram of the present invention incorporates or includes a number of features which allow safer, more efficient Rig-Up operations. The jacking frame, by using a single, movable columnar support, allows greater access to the BOP and the well. In addition, the jacking frame allows the injector, goosemech and related equipment to be quickly and easily moved, thereby allowing access, for instance, crane access, to the well. The jacking frame may carry some or all of the BOP stack, as may be required for a particular operation. This is particularly useful where certain hangoffs are desired. In addition, the jacking frame may be used to carry the BOP stack off the wellhead.
In the preferred embodiment, the BOP transport skid houses a triple BOP stack, a shear seal or safety head as required, and an additional pipe/slip ram. The transport skid is designed to minimize the required steps for assembling the well control stack. In those cases where a safety-head shear seal ram is required, the ram is designed to be tilted in order to fit through the rig floor opening. In this configuration, the safety head will travel coupled to the pipe/slip ram. In one embodiment, the ram assembly may travel with the rams oriented in the vertical position, will be lifted, dropped through the deck, rotated and fastened to the wellhead. The triple BOP, riser and BOP work platform will travel assembled in the horizontal position and will be pivoted into place on the rig. The working platform is also integral and is folded into the skid envelope.
Crash frames may be provided during transportation and storage.
Various other skids are supplied as required for the operation, as described above.